1. Field of the Invention
This invention relates to fluid handling apparatus. More particularly, this invention relates to an integral check valve of the type that are used in windshield/glass washer nozzles.
2. Description of the Related Art
Windshield washer spray systems are well known in the art. Generally, they consist of windshield washer nozzles that are mounted in the hood of a vehicle. Fluidic inserts in these nozzles cause a jet of windshield washer fluid to be oscillated laterally so as to project a fan spray of windshield washer droplets that impinge over the whole lateral width of a windshield.
Check valves are typically included in the washer fluid feed lines of these nozzles to eliminate “drool” due to: (a) dynamic loads on the windshield washer system when the car is moving, and (b) static loads on the hood-mounted system when the car is stationary, but its hood is lifted.
These check valve are designed so as to have a threshold or cracking pressure below which no fluid will flow through the nozzle. Moreover, such check valves prevent air from entering the system through the nozzle, which thereby prevents fluid from draining back into the reservoir for the washer fluid. This permits a faster response time since the response time is not slowed due to the nozzle's feed tubes draining back into the reservoir after the system has been actuated. With the feed tubes remaining “primed,” the response time of these nozzles is very fast. Finally, the relatively high cracking pressure of these nozzles provides a “crisp start-up and shut-off” which means that the number of drops from such nozzles that land on surfaces other than the glass at which they are directed is very small.
For such windshield washer applications, a washer nozzle typically includes a housing which is welded to an elbow or hose nipple after assembling the check valve components inside the elbow. The initial designs for washer nozzles were based on “ball and spring,” or soft seat systems.
An example of such a Bowles Fluidics Corporation system that was commercially used for many years is given in FIG. 1 from U.S. Pat. No. 5,636,794 to Hess and Marsden. It is seen to comprise a molded housing 10 having a fluidic oscillator insert chamber 11 adapted to receive a molded silhouette member 12 which has a fluidic oscillator silhouette molded in face 13 and peripheral side and edge surfaces which are adapted to make a scaling engagement with the interior walls 14 of chamber 11. The fluidic oscillator has a power nozzle PN which is adapted to be aligned with the wash fluid inlet passage 15. Wash fluid inlet passage 15 is coupled to a second wash fluid inlet passage 16. In the embodiment shown, the oscillator chamber 11, inlet passage 15 and inlet passage 16 are made in the molding process by pins which are withdrawn to leave the passages. A ball 17 is forcibly inserted into the enlarged end 18 of wash fluid passage 15 to seal it.
The portions 19, 20 are designed to accommodate a particular opening in the hood or other mounting structure of a vehicle for mounting purposes and is not particularly relevant to the present invention.
As shown in FIG. 1, the second wash fluid passage 16 is formed in a nipple 21 which has an annular rib 22 molded therein. A check valve assembly 23 is included in a hose nipple 24. The check valve assembly 23 includes an annular shoulder 25 formed on an inward portion of inlet nipple 21 and includes a spring 26 urging ball valve element 27 into a valve seat 28 formed on the interior wall of wash fluid inlet passage 29. Check valve assembly 23 is assembled by placing the spring on the shoulder 25 and fitting the ball 28 into the seat and then forcing the annular connection collar 30 onto the nipple 21 with annular rib 22 seated in annular groove 31.
It will be appreciated that the design of FIG. 1 is, in effect, a two-piece nozzle housing where the two pieces are welded or glued together along the nipple 21 and the connection collar 30. That is, the line “L” where the two parts are joined together can leak and this also requires an extra assembly process.
The “ball and spring” check valves were found to suffer from several problems. These included: (a) poor sealing between the hard metal surface and hard plastic surfaces, (b) material corrosion in the contact area, which may lead to a stuck check valve, (c) cocking of the spring assembly in the housing which causes operational problems with the valves, (d) cumbersome manual assembly, (e) poor weld strength in joint linking the housing and the elbow due to the thin wall thicknesses and structural discontinuities in this area, and (f) difficulty in molding the complex plastic parts which comprise the housing and elbow.
This “ball and spring” check valve was improved upon by the introduction of the check valve shown in FIGS. 2-3(a)-(b) which are also from U.S. Pat. No. 5,636,794. In this check valve, the wash fluid feed tube 50 has an internal shoulder 51 which is deep within wash fluid input tube 50 for receiving the base of check valve spring 26′. A ball check valve 28′ is urged or biased by spring 26′ into engagement with valve seat 53 formed on the downstream end of tubular insert member 54 which has an external surface 55 having a diameter D at least sufficient to form an elongated wash fluid seal 56 with the annular walls 57 defining the wash fluid flow path. The tubular insert 54 can be adjusted in length LI (or its depth of insertion adjusted) to thereby adjust the cracking pressure e.g., the pressure when the valve unseats and wash fluid is allowed to flow to the windshield washer nozzle. Thus, by adjusting the length LI of tubular insert 54, the cracking pressure can be adjusted without any other structural change in the assembly.
For this check valve, the hose or rubber tube 60 is telescoped over the outer end of input tube 54 and is retained in place by barb 61. The rubber hose 60 seals along the external surface and is the only seal that is required thereby eliminating seals such as the seal between the coupling element 30 and nipple 21 of the prior art design shown in FIG. 1.
FIGS. 3(a)-(b) disclose other embodiments in which the shape of the check valve element is other then that of a ball. In FIG. 3(a), the check valve 66 has a conical external surface and a centering projection 65 on its downstream end. In FIG. 3(b), the check valve 75 has a rounded, mushroom-shape external surface and a centering projection 65 on its downstream end.
A further improvement to these types of check valves at Bowles Fluidics has been the replacement of these ball and other types of check valves with a “carrier assembly,” consisting of a piston and seal, such as that shown in FIG. 4(a). More details of these piston and seal elements are shown in FIGS. 4(b)-(c). However, this configuration has been found to be cumbersome to manually assembly, and is not a manufacturing friendly design. Additionally, welding and molding of these parts has continued to be a problem.
Thus, despite the prior art, there still exists a continuing need for improvements in the design of check valves for a wide range of nozzle applications.
3. Objects and Advantages
Recognizing the need for the development of improved check valves, the present invention is generally directed to satisfying the needs set forth above and overcoming the disadvantages identified with prior art devices.
It is an object of the present invention to provide an improved check valve for a windshield washer system that is easier to manufacture than those previously and currently used.
It is another object of the present invention to provide an improved check valve for a windshield washer system that requires less manual labor to assemble.
It is yet another object of the present invention to provide an improved check valve for a windshield washer system that is easier to mold and weld than those previously and currently used.
Other objects and advantages of the present invention will become readily apparent as the invention is better understood by reference to the accompanying drawings and the detailed description that follows.